This invention relates to a method of fabricating a structural member by electro slag forming, and more particularly to a method of fabricating a unitary structural member, in which a part of the unitary structual member is formed, on the other part thereof which is previously made in a certain shape, by electro slag forming.
In a structural member such as a wicket gate for a water turbine, different materials are often required in its different portions. The wicket gate comprises a vane portion, two journal portions on the both sides of the vane portion, and a stem portion extending from one of the journal portions. The vane portion is disposed in a water flow, with the both journal portions being rotatably supported by bearings, and moved by the stem portion which is mechanically connected to a driving apparatus so as to be opened and closed. The vane and journal portions are in contact with a water flow, and the journal portions each are subjected to friction caused by the bearing. Therefore, the vane and journal portions have been made of corrosion-resisting and wear-proof material. The stem portion also is made of the same material as the vane. For the stem portion, such a material is not necessary because it is enough as long as force from the driving apparatus is transmitted to the vane portion. Thus, in the wicket gate, different materials are required in different portions.
A conventional wicket gate, however, is made unitarily of the same material by casting. According to the casting, in order to form a more reliable wicket gate, the whole wicket gate must be made of a more reliable material, which is very expensive.
Further, the casting necessitates a plurality of processes for forming the wicket gate, including manufacture of wooden and sand patterns, casting, sand removing, etc. Additionally, the cast wicket gate has defects such that blow holes are easily made in the cast wicket gate.
Thus, it is desired that high quality of the wicket gate is made more economically.